Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$59.72	8.548%	$64.8249	$64.82	$64.80	$64.80
Purchase #2	$148.52	3.658%	$153.9529	$153.95	$153.95	$154.00
Purchase #3	$175.88	5.392%	$185.3634	$185.36	$185.35	$185.40
Purchase #4	$36.79	7.619%	$39.593	$39.59	$39.60	$39.60
Purchase #5	$82.67	13.597%	$93.9106	$93.91	$93.90	$93.90
Purchase #6	$125.96	9.241%	$137.6	$137.60	$137.60	$137.60
Purchase #7	$31.32	6.418%	$33.3301	$33.33	$33.35	$33.30
7 purchase totals =	$660.86		$708.5749	$708.56	$708.55	$708.60